The Development And Design Of Transient Electromagnetic Software

Transient electromagnetic (TEM) method is an important time domain electromagnetic prospecting method, which transmits the primary impulse electromagnetic field by the non-earthed loop or earthed electrode source. And space and time distribution of the secondary eddy current is observed at the absence of the primary electromagnetic field by earthed loop or earthed electrode, which is used to solve the problems related to geology. TEM has more advantages than frequency electromagnetic method in some aspects, however, the complexity of electromagnetic theory results in high-dimensional forward and inversion quantitative interpretation methods under the study. Another, present processing software are complex, time-consuming and difficult to adapt to a large amount of field data in real-time imaging, therefore it plays very strong and actual significance to research and develop transient electromagnetic processing and interpretation software with the rapid inversion technique.There are six chapters in this paper, which can be divided into four parts: The first part is introduction, which contains the history about development of transient electromagnetic method and the current situation of domestic transient electromagnetic processing software. The second part includes the second, third, forth chapter, which respectively introduces respectively R-T mechanism of TEM source and response process, the theory for forward modeling of homogeneous half space, one dimensional layer earth and the rapid inversion technique,the development and design of software etc.. The third part is made up of the fifth and sixth chapter, design ideas and method for the transient electromagnetic processing software has been described in detail. The fourth part is conclusion, and some ideas of further research are put forward.Forward and inversion modeling of homogeneous half space and one dimensional layer earth have been solved. But response function of the two and three dimensional layer earth model is complex, excessively costly in computation, therefore at present is so few solutions. According to what I have known, there is Wang Hua Jun (2003) and Xiong Bin (2006) who realized simulating calculation of TEM 2.5D finite-element method, Mao Lifeng(2007) who finished simulating calculation of TEM 3D finite difference method in ultra-broadband domain. The simulating calculation of TEM 2.5D finite-difference method with Guptasarma algorithm is used in this paper, which has faster computation speed and effectively restrains the late-time vibration phenomenon. For simplicity, based on smoking ring theory of Nabighian, we use rapid electrical resistivity tomography in the inversion, which can obtain resistivity-depth profile of TEM data. This method doesn't need the initial model and the speed of inversion is very fast.Comprehensive analysis of TEM data format and processing explanation method, combining theory and practice, according to actual needs and requirements of software engineering, object oriented programming idea and method is adopted to develop software with full function, reasonable structure, friendly graphical user interface and environments.It is very important to select the software development platform and development tool. Windows is an operating system which is easy to use, which can enhance work efficiency, and greatly shorten the software development cycle and have a good human computer interface. Therefore Windows is used as a development platform in our software development. Visual C++ 6.0 is adopted as user interface development tool, forward and inversion makes use of Compaq Visual Fortran6.5, and mapping by MATLAB.TEM processing software consists of six sub-modules: data management module, data editing module, forward module, rapid electrical resistivity imaging module,windows modeling module, mapping module,and the six sub-modules are closely related. Data management module is for user to manage data. Data editing module provide qualified data to electrical resistivity imaging module. Forward module is for the simulating calculation of TEM 2.5D. Rapid electrical resistivity imaging module provides right data to mapping module. Windows modeling module is for drawing the model of TEM 2.5D forward on the desktop.Data management module and Windows modeling module adopt the VC++ 6.0, among it, Windows modeling module adopt the GDI+(Graphics Device Interface Plus) to accomplish module development.Data editing module adopt the VC++ 6.0 and TEE CHART. The TEE CHART is easy to use which has powerful function and fully reflects the characteristics of the object-oriented. Apparent resistivity curve is showed by Chart component. Acquisition data will be with inevitable interference, so the apparent resistivity curve is unsmoothed. Then the apparent resistivity curve should be edited smoothly to provide qualified data to electrical resistivity imaging module.The user interface of forward module and electrical resistivity imaging module designed by VC++ 6.0 and the 2.5D forward and inversion using Fortran, will bring advantages of two development tool which will involve in mixed programming, namely ,using two or more of the programming language to build the program modules. Utilizing the DLL can achieve two kind of different programming languages calling each other. The forward and inversion module is programmed by Fortran,so we can compile the forward and inversion program for effectively using present procedure and reduce unnecessary duplication work. The user interface calls DLL to enhance executive efficiency.The mapping module adopts Visual C++ and MATLAB mixed programming. MATLAB compiler can translate the M file to DLL file, the user interface calls DLL to draw a picture. It full use of the powerful drawing function of MATLAB to avoid development drawing software again.